The broad objectives of the proposed research are to gather further evidence for the identification of certain amino acids as neurotransmitters, and to examine pharmocological and physiological factors which influence their release from neural tissue. Emphasis will be placed on studies of the release of endogenous amino acids from he intact retina during perfusion of the vitreous. Complimentary and comparative studies will be performed to examine the release of endogenous amino acids from neural tissues incubated in vitro. These model systems will be used for the study of the action of neurotrophic drugs such as penicillin and baclofen, agents which are presumed to interfere with synaptic transmission mediated by amino acid transmitters.